Optiplex 990 with 2 Radeon HD 6350 - 4 monitors not working

Then why does Dell sell it this way?  I ordered it from Dell with 2 cards in it...

4 monitors only works on a single card.   The 990 is NOT an AMD CrossFireX Ready motherboard.

AMD CrossFireX technology in greater than dual mode is not supported with AMD Radeon™ HD 6350 graphics products.

Visiontek HD5570 SFF 4-port VGA VHDCI 1 GB x16 ...

VisionTek ATI Radeon HD 5570 1 GB SFF 4-Port VHDCI x16 PCI Express Graphics Card 900345 (Black/Red)

All of the Optiplex 990 Dell Radeon HD6350s come with a DMS-59 port. So can you describe what dongle your plugging into the DMS-59 ports?

This is somewhat confusing on the sales site -
Dell OptiPlex 990 includes both a native VGA and a native DisplayPort connector on the Minitower, Desktop and Small Form Factor chassis. For customers interested in DVI support with integrated graphics, a DP to DVI adapter cable below will convert the native DisplayPort connector into DVI . Dual independent displays can be supported with integrated graphics via VGA and DisplayPort. Dual graphic combinations are available utilizing dual PCIe x16 slots (one routed as a PCIe x4).

Is that saying you can use VGA and DP (DisplayPort) while also plugging in monitors to the 6350 via DMS-59 to DVI dongle?

I got it to work by turning off Crossfire in the Catalyst Control Panel.  That being said, I think its a bad form for Dell to sell them this way if you can't get Crossfire to work across the 4 monitors.

AMD CrossFireX technology in greater than dual mode is not supported with AMD Radeon™ HD 6350 graphics products.

Not all features may be supported on all components or systems . AMD Eyefinity technology works with games that support non-standard aspect ratios, which is required for panning across multiple displays. To enable more than two displays, additional panels with native DisplayPort connectors, and/or DisplayPort compliant active adapters to convert your monitor’s native input to your cards DisplayPort or Mini-DisplayPort connector(s), are required. SLS (Single Large Surface) functionality requires an identical display resolution on all configured displays. AMD PowerPlay™ and AMD Accelerated Parallel Processing (APP) are technology platforms that include a broad set of capabilities offered by certain AMD Radeon™ HD GPUs.

Not all products have all features and full enablement of some capabilities and may require complementary products.

I am having the same problem, I have disabled crossfire and still when I plug in a third monitor on the second card all of my monitors go blank and I have to reboot to get them back.